The tape driver of a conventional device, for example, a video tape recorder (VTR) is formed in several places with photointerrupters which are composed of light emitting diodes LED and photodiodes PD, and which serve for the acknowledgement of the insertion of a cassette, the detection of the loosening of a tape, etc. They require electric wiring and are often mounted in places distant from a printed circuit board, so that wiring leads must be laid on a chassis. The job of laying the wiring leads is difficult of automation. Moreover, components which detest electric noise, such as magnetic heads, are mounted on the chassis, and it must be avoided to the utmost to lay the wiring leads for the sensors near the components.
It is therefore considered to employ a photosensor, for example, a photosensor which is disclosed in the official gazette of Japanese patent application Laid-open No. 57-796 issued on Jan. 5, 1982. In the sensor described in the above official gazette, however, the section between a light source and a part to-be-sensed and the section between the part to-be-sensed and a light receiving portion are independent as optical fiber paths or optical guide paths which are separate from each other. Besides, optical fiber guide paths and optical delay lines are included in correspondence with a plurality of parts to-be-sensed, and complicated wiring is inevitably involved according to the arrangement of the plurality of parts to-be-sensed.